<p>Two other basic types of data in Swift are doubles and booleans, and you’ll be using them a lot.</p>
<p>“Double” is short for “double-precision floating-point number”, and it’s a fancy way of saying it holds fractional values such as 38.1, or 3.141592654.</p>
<p>Whenever you create a variable with a fractional number, Swift automatically gives that variable the type <code>Double</code>. For example:</p>
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<p><span class="keyword">var</span> pi <span class="operator">=</span> <span class="number">3.141</span></p>
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<p>Doubles are different from integers, and you can’t mix them by accident.</p>
<p>As for booleans, they are much simpler: they just hold either true or false, and Swift will automatically assign the boolean type to any variable assigned either true or false as its value.</p>
<p>For example:</p>
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<p><span class="keyword">var</span> awesome <span class="operator">=</span> <span class="boolean">true</span></p>
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